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Re: segment fault when running xfs_check -s

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: segment fault when running xfs_check -s
From: xiaowei hu <xiaowei.hu@xxxxxxxxxx>
Date: Tue, 22 Jun 2010 15:17:00 +0800
Cc: xfs@xxxxxxxxxxx, wen.gang.wang@xxxxxxxxxx
In-reply-to: <20100621053803.GK6590@dastard>
Organization: Oracle
References: <1277088918.20616.81.camel@redfuture-desktop> <20100621053803.GK6590@dastard>
Reply-to: xiaowei.hu@xxxxxxxxxx
Hi Dave,

I tried this patch,it fixes this bug, thank you very much:)

Regards,
Xiaowei



On Mon, 2010-06-21 at 15:38 +1000, Dave Chinner wrote:
> On Mon, Jun 21, 2010 at 10:55:18AM +0800, xiaowei hu wrote:
> > Hi,
> > 
> > Recently I was playing with xfsprogs, and did some test on xfs_check
> > tools in this mothod:
> > 1.make a xfs fs on one partition.
> > mkfs.xfs -f /dev/sda2
> > 2.randomly modify some blocks on this volume using xfs_db.
> > xfs_db -x -c blockget -c "blocktrash -3 -s 36 -n 81" /dev/sda2
> > 3.run xfs_check -s
> > xfs_check -s /dev/sda2
> > 
> > the output saying:
> > [root@test1 ~]# xfs_check -s /dev/sda2
> > bad version number 0x78 for inode 135
> > bad magic number 0xa855 for inode 154
> > bad magic number 0x5024 for inode 165
> > /usr/local/bin/xfs_check: line 28:   769 Segmentation fault      xfs_db
> > $DBOPTS -F -i -p xfs_check -c "blockget$OPTS" $1
> > 
> > if I run xfs_check without -s option, don't have this fault.
> > 
> > Is this a known problem?
> 
> No.
> 
> > I tried the latest code ,also have this problem.
> 
> Yeah, the code determining whether to output a message is broken:
> 
> 2651         if (!isfree) {
> 2652                 id = find_inode(ino, 1);
> 2653                 bno = XFS_INO_TO_FSB(mp, ino);
> 2654                 blkmap = NULL;
> 2655         }
> 
> find_inode() checks a list created by the "-i <ino #>" command line
> option, so will always return NULL for this test case. Most of the checks
> do this:
> 
> 2657                 if (!sflag || isfree || id->ilist || CHECK_BLIST(bno))
> 
> sflag is set by the "-s" command line option, which is why this
> problem requires that to be set - the output checks don't get past
> this otherwise.
> 
> isfree is a parameter passed into to say whether the inode is
> allocated or not. The code hence assumes that if !isfree, then id !=
> NULL, which is certainly not the case. Hence it can blow up if id =
> NULL.
> 
> The line it crashed on:
> 
> 2670         if (isfree) {
> 2671                 if (idic.di_nblocks != 0) {
> 2672  >>>>>>                 if (!sflag || id->ilist || CHECK_BLIST(bno))
> 
> Looks like a clear case of copy-n-paste error - if isfree is set, the
> id _must_ be null and we go kaboom.
> 
> It looks like none of the code in this function actually checks for
> whether id is valid or not after find_inode and dereferencing the
> reurn pointer.
> 
> The patch below should fix the problem.
> 
> Cheers,
> 
> Dave.
> -- 
> Dave Chinner
> david@xxxxxxxxxxxxx
> 
> ---
>  db/check.c |   29 ++++++++++++++++-------------
>  1 files changed, 16 insertions(+), 13 deletions(-)
> 
> diff --git a/db/check.c b/db/check.c
> index 7620d9c..e0dcf63 100644
> --- a/db/check.c
> +++ b/db/check.c
> @@ -2619,6 +2619,7 @@ process_inode(
>       xfs_qcnt_t              ic = 0;
>       xfs_qcnt_t              rc = 0;
>       xfs_dqid_t              dqprid;
> +     int                     v = 0;
>       static char             okfmts[] = {
>               0,                              /* type 0 unused */
>               1 << XFS_DINODE_FMT_DEV,        /* FIFO */
> @@ -2653,15 +2654,16 @@ process_inode(
>               bno = XFS_INO_TO_FSB(mp, ino);
>               blkmap = NULL;
>       }
> +     v = (!sflag || (id && id->ilist) || CHECK_BLIST(bno));
>       if (idic.di_magic != XFS_DINODE_MAGIC) {
> -             if (!sflag || isfree || id->ilist || CHECK_BLIST(bno))
> +             if (isfree || v)
>                       dbprintf(_("bad magic number %#x for inode %lld\n"),
>                               idic.di_magic, ino);
>               error++;
>               return;
>       }
>       if (!XFS_DINODE_GOOD_VERSION(idic.di_version)) {
> -             if (!sflag || isfree || id->ilist || CHECK_BLIST(bno))
> +             if (isfree || v)
>                       dbprintf(_("bad version number %#x for inode %lld\n"),
>                               idic.di_version, ino);
>               error++;
> @@ -2669,7 +2671,7 @@ process_inode(
>       }
>       if (isfree) {
>               if (idic.di_nblocks != 0) {
> -                     if (!sflag || id->ilist || CHECK_BLIST(bno))
> +                     if (v)
>                               dbprintf(_("bad nblocks %lld for free inode "
>                                        "%lld\n"),
>                                       idic.di_nblocks, ino);
> @@ -2680,21 +2682,22 @@ process_inode(
>               else
>                       nlink = idic.di_nlink;
>               if (nlink != 0) {
> -                     if (!sflag || id->ilist || CHECK_BLIST(bno))
> +                     if (v)
>                               dbprintf(_("bad nlink %d for free inode 
> %lld\n"),
>                                       nlink, ino);
>                       error++;
>               }
>               if (idic.di_mode != 0) {
> -                     if (!sflag || id->ilist || CHECK_BLIST(bno))
> +                     if (v)
>                               dbprintf(_("bad mode %#o for free inode 
> %lld\n"),
>                                       idic.di_mode, ino);
>                       error++;
>               }
>               return;
>       }
> +
>       if (be32_to_cpu(dip->di_next_unlinked) != NULLAGINO) {
> -             if (!sflag || isfree || id->ilist || CHECK_BLIST(bno))
> +             if (v)
>                       dbprintf(_("bad next unlinked %#x for inode %lld\n"),
>                               be32_to_cpu(dip->di_next_unlinked), ino);
>               error++;
> @@ -2704,27 +2707,27 @@ process_inode(
>        */
>       if ((((idic.di_mode & S_IFMT) >> 12) > 15) ||
>           (!(okfmts[(idic.di_mode & S_IFMT) >> 12] & (1 << idic.di_format)))) 
> {
> -             if (!sflag || id->ilist || CHECK_BLIST(bno))
> +             if (v)
>                       dbprintf(_("bad format %d for inode %lld type %#o\n"),
>                               idic.di_format, id->ino, idic.di_mode & S_IFMT);
>               error++;
>               return;
>       }
>       if ((unsigned int)XFS_DFORK_ASIZE(dip, mp) >= XFS_LITINO(mp))  {
> -             if (!sflag || id->ilist)
> +             if (v)
>                       dbprintf(_("bad fork offset %d for inode %lld\n"),
>                               idic.di_forkoff, id->ino);
>               error++;
>               return;
>       }
>       if ((unsigned int)idic.di_aformat > XFS_DINODE_FMT_BTREE)  {
> -             if (!sflag || id->ilist)
> +             if (v)
>                       dbprintf(_("bad attribute format %d for inode %lld\n"),
>                               idic.di_aformat, id->ino);
>               error++;
>               return;
>       }
> -     if (verbose || id->ilist || CHECK_BLIST(bno))
> +     if (verbose || v)
>               dbprintf(_("inode %lld mode %#o fmt %s "
>                        "afmt %s "
>                        "nex %d anex %d nblk %lld sz %lld%s%s%s%s%s%s%s\n"),
> @@ -2844,20 +2847,20 @@ process_inode(
>       }
>       totblocks = totdblocks + totiblocks + atotdblocks + atotiblocks;
>       if (totblocks != idic.di_nblocks) {
> -             if (!sflag || id->ilist || CHECK_BLIST(bno))
> +             if (v)
>                       dbprintf(_("bad nblocks %lld for inode %lld, counted "
>                                "%lld\n"),
>                               idic.di_nblocks, id->ino, totblocks);
>               error++;
>       }
>       if (nextents != idic.di_nextents) {
> -             if (!sflag || id->ilist || CHECK_BLIST(bno))
> +             if (v)
>                       dbprintf(_("bad nextents %d for inode %lld, counted 
> %d\n"),
>                               idic.di_nextents, id->ino, nextents);
>               error++;
>       }
>       if (anextents != idic.di_anextents) {
> -             if (!sflag || id->ilist || CHECK_BLIST(bno))
> +             if (v)
>                       dbprintf(_("bad anextents %d for inode %lld, counted "
>                                "%d\n"),
>                               idic.di_anextents, id->ino, anextents);


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